Radial Y capacitors made with too small pitch

[treez]

Because of the size of the restring in the footprint of these Y2 capacitors, (even the 7.5mm pitch ones) , they cannot singly be placed across the isolation barrier of an offline SMPS, since they would violate the rule of 8mm for isolation barrier.

DE2E3SA222MJ3BT02F
https://www.mouser.co.uk/datasheet/2/281/DE2_SA_T0_F_E-1115418.pdf


So therefore, they end up getting put in two-in-series across the isolation barrier…however, that means you have more stray inductance…..and this isnt good because common mode noise is of high frequency (typically >>1MHz), and therefore, the capacitor will look more like an inductor.
Why don’t they more commonly make these kind of capacitors with a pitch of 10mm? Then they could be used singly.

In fact, why dont people make more surface mount y caps?...because they would have even less stray inductance and be better for the high frequency common mode noise

 

[barry]

So, you found a capacitor that doesn't meet your requirements, and then start yet another one of your rants instead of searching and finding PLENTY of Y2 capacitors that have greater than 8mm lead spacing. Like this: https://www.vishay.com/docs/23104/30lvs.pdf

Or this:

 

[FvM]

Ever heard about milled slots?

 

[betwixt]

Just about every 'decent quality' SMPS I have seen has milled slots under the capacitor and also under feedback opto-couplers, even though they usually DO have sufficient clearance.

Brian.

 

[FvM]

Why is it so that almost any designer tries to learn from existing devices, adapting state of the art as least as a starting point. But you are so often re-inventing the wheel?

 

[barry]

Why is it so that almost any designer tries to learn from existing devices, adapting state of the art as least as a starting point. But you are so often re-inventing the wheel?

And then complaining that your square wheel doesn't work and why don't manufacturers make round wheels.

 

[treez]

Thanks, and so you dont think there is any mileage in using two series Y capacitors in order to increase mains transient withstand?
I must admit, you see two Y caps in series across the isolation barrier so often, that i often wonder if they have done it to increase transient withstand voltage?

 

[FvM]

I still don't understand your contributions in this thread. My answer to your previous Y capacitor thread was already linking capacitors with 10 mm pitch, so there is a simple solution if you want higher creepage without milling the PCB. But if small form factor is an objective, why don't you use the suggested solution?

https://www.edaboard.com/showthread...adial-Y-capacitors-for-offline-power-supplies

 

[treez]

yes, thanks, to be honest, i wonder how many people use 2 y caps in series to increase mains transient protection?

 

[betwixt]

I doubt any do. Half the value and twice the risk! If one cap breaks down, the full voltage appears across the other one and breaks that too. In fact it's doubtful that the same voltage would appear across the capacitors anyway, differences in their values would result in unequal charge (= voltage) distribution between them.

Brian.